System and method for generating electric power from a rotating tire&#39;s mechanical energy

ABSTRACT

A tire assembly with integrated power generation features includes one or more piezoelectric devices configured to generate electric charge therein upon being subjected to mechanical strains associated with flexure of tire or wheel components. The piezoelectric device may be incorporated in a variety of tire structures and in many different locations. In pneumatic tire structures, the piezoelectric device and related electronics may be embedded in crown or sidewall locations among such selected components as the exterior tread portion, first and second steel belts of a belt package, carcass, cap ply portion, inner liner, zone base, etc. The piezoelectric device with optional rubber casing may also be attached to such locations as the inner liner and tire exterior. Piezoelectric devices may also be integrated with a tire and safety support combination that is configured to operate in an extended mobility mode when the tire structure loses air pressure. Piezoelectric devices may alternatively be integrated with a non-pneumatic structurally supported tire such as one including a reinforced annular band, a plurality of web spokes extending transversely across and radially inward from the annular band, a mounting band at the inner end of the web spokes and a tread portion disposed on the annular band.

PRIORITY CLAIM

This application claims priority as a Continuation-In-Part Applicationof previously filed U.S. Patent Application entitled “SYSTEM AND METHODFOR GENERATING ELECTRIC POWER FROM A ROTATING TIRE'S MECHANICAL ENERGYUSING PIEZOELECTRIC FIBER COMPOSITES,” with inventors John D. Adamsonand George P. O'Brien, assigned U.S. Ser. No. 10/143,535, filed on May10, 2002 now U.S. Pat. No. 6,807,853, and which is incorporated hereinby reference for all purposes. This application also claims priority asa Continuation-In-Part Application of previously filed U.S. PatentApplication entitled “SYSTEM AND METHOD FOR GENERATING ELECTRIC POWERFROM A ROTATING TIRE'S MECHANICAL ENERGY,” with inventors John D.Adamson and George P. O'Brien, assigned U.S. Ser. No. 10/850,860, filedon May 21, 2004 now U.S. Pat. No. 7,096,727, and which is alsoincorporated herein by reference for all purposes.

FIELD OF THE INVENTION

The present invention generally concerns a system and method ofsubjecting piezoelectric structures to the mechanical energy of tirerotation, thereby generating electric power for integrated tireelectronics. Piezoelectric technology is utilized to convert mechanicalstrain associated with the flexure of tire or wheel components toelectric charge that is then conditioned and stored in an energy storagedevice. Sufficient accumulations of such stored energy can then powerelectronic systems including components for identifying various physicaltire parameters as well as radio frequency (RF) transmission devices.

BACKGROUND OF THE INVENTION

The incorporation of electronic devices with tire structures yields manypractical advantages. Tire electronics may include sensors and othercomponents for obtaining information regarding various physicalparameters of a tire, such as temperature, pressure, number of tirerevolutions, vehicle speed, etc. Such performance information may becomeuseful in tire monitoring and warning systems, and may even potentiallybe employed with feedback systems to regulate proper tire pressurelevels.

U.S. Pat. No. 5,749,984 (Frey et al.) discloses a tire monitoring systemand method that is capable of determining such information as tiredeflection, tire speed, and number of tire revolutions. Another exampleof a tire electronics system can be found in U.S. Pat. No. 4,510,484(Snyder), which concerns an abnormal tire condition warning system. U.S.Pat. No. 4,862,486 (Wing et al.) also relates to tire electronics, andmore particularly discloses an exemplary revolution counter for use inconjunction with automotive and truck tires.

Yet another potential capability offered by electronics systemsintegrated with tire structures corresponds to asset tracking andperformance characterization for commercial vehicular applications.Commercial truck fleets, aviation crafts and earthmover/mining vehiclesare all viable industries that could utilize the benefits of tireelectronic systems and related information transmission. Tire sensorscan determine the distance each tire in a vehicle has traveled and thusaid in maintenance planning for such commercial systems. Vehiclelocation and performance can be optimized for more expensiveapplications such as those concerning earth mining equipment. Entirefleets of vehicles could be tracked using RF tag transmission, exemplaryaspects of which are disclosed in U.S. Pat. No. 5,457,447 (Ghaem etal.).

Such integrated tire electronics systems have conventionally beenpowered by a variety of techniques and different power generationsystems. Examples of mechanical features for generating energy from tiremovement are disclosed in U.S. Pat. No. 4,061,200 (Thompson) and U.S.Pat. No. 3,760,351 (Thomas). Such examples provide bulky complex systemsthat are generally not preferred for incorporation with modern tireapplications.

Some tire electronics systems have been powered by various piezoelectricdevices. U.S. Pat. No. 6,438,193 (Ko et al.) discloses a self-poweredtire revolution counter that includes a piezoelectric element mounted ina tire in a manner so as to be subjected to periodic mechanical stressesas the tire rotates and to provide periodic pulses in response thereto.Yet another example of piezoelectric devices used for powering tireelectronics systems is disclosed in U.S. Pat. No. 4,510,484 (Snyder),which concerns a piezoelectric reed power supply symmetricallyconfigured about a radiating center line of a tire.

Another typical solution for powering tire electronics systemscorresponds to the use of a non-rechargeable battery, which inherentlyprovides an inconvenience to the tire user since proper electronicssystem operation is dependent on periodic battery replacement.Conventional batteries also often contain heavy metals that are notenvironmentally friendly and which present disposal concerns, especiallywhen employed in highly numerous quantities. Still further, batteriestend to deplete their energy storage quite rapidly when poweringelectronic applications characterized by complex levels offunctionality. Battery storage depletion is especially prevalent inelectronic systems that transmit information over a relatively fardistance such as from truck wheel locations to a receiver in the truckcabin. Even when batteries are used in electronics systems that transmitfrom wheel locations to a closer receiver location, information is thentypically relayed via hard-wire transmission medium from the RF receiverlocation to the vehicle cab thus requiring the installation ofadditional and often expensive communications hardware in a vehicle.

Yet another known method for deriving power for tire monitoring systemsrelates to scavenging RF beam power with an interrogation antenna inclose proximity to a tire and integrated electronic features. Energythat is radiated from the antenna is scavenged to power the electronics,which must often be very specialized ultra-low-power electronics limitedto within a few microwatts. Interrogation antennas employed inconjunction with beam-powered electronics must typically be placed inrelatively close proximity (within about two feet) to each wheel welldue to limited transmission ranges. This typically requires multipleinterrogation antennas per vehicle, thus adding to potential equipmentcosts. Each antenna is also quite susceptible to damage from roadhazards, and thus for many reasons may not be the most desirablesolution for powering certain tire electronic applications.

The disclosures of all of the foregoing United States patents are herebyfully incorporated into this application for all purposes by referencethereto. While various tire electronics systems and power generationsystems therefor have been developed, no design has emerged thatgenerally encompasses all of the desired characteristics as hereafterpresented in accordance with the subject technology.

SUMMARY OF THE INVENTION

In view of the recognized features encountered in the prior art andaddressed by the present subject matter, an improved system and methodfor powering electronic systems integrated within a tire structure hasbeen developed. Piezoelectric technology is utilized to convertmechanical strains associated with tire flexure to electric charge thatis then conditioned and stored in one or more energy storage devices.Sufficient accumulations of such stored energy can then power electronicsystems including components for identifying various physical tireparameters as well as radio frequency (RF) transmission devices.

In accordance with more particular aspects of the disclosed technology,it is an object of the present subject matter to provide a tire withintegrated self-powered electronic components. Such electroniccomponents are self-powered by energy harvested from integratedpiezoelectric structures, and may correspond with numerous electronicapplications. One exemplary electronic application concerns a tiremonitoring system designed to measure and transmit information regardingtire conditions such as pressure and temperature, as well as otherinformation such as the number of tire revolutions or general tireidentification variables.

Various features and aspects of the subject tire electronics system andspecialized power generating device offer a plurality of advantages. Thedisclosed technology provides for a self-powered tire electronics systemthat is not dependent on replacement of batteries. Although batteriesand battery-operated devices may still be incorporated with aspects ofthe present subject matter, many complications regarding tireelectronics that are solely powered by batteries are obviated inaccordance with the disclosed technology.

Another advantage of the present subject matter is that a tiremonitoring system is provided that reduces the amount of required signalhardware relative to conventional tire monitoring systems. By providinga tire monitoring system that is self-powered, no scavenger antennas ormultiple receiver locations with additional hardwire connections arerequired. Components of such a tire monitoring system can be integratedwithin each individual tire structure on a given vehicle such that asingle receiver (typically located in a vehicle cabin) is capable ofacquiring information transmitted by each tire's integrated electronics.

Yet another advantage of the present subject matter is that there arefewer limitations regarding the type and amount of electronic equipmentcapable of utilization within tire and wheel assembly structures. Tireelectronics powered by conventional methods other than as in accordancewith the disclosed piezoelectric technology are often limited toultra-low power devices. Devices in accordance with the disclosedtechnology are not necessarily subject to such extreme powerlimitations. This advantage further facilitates greater functionality oftire electronics, as more components and/or higher-level equipment maypotentially be utilized.

A still further advantage of the present subject matter is that thedisclosed system and method for generating power and utilizing suchpower can be used in accordance with a variety of existing applications.Measurement capabilities, monitoring and warning systems, vehiclefeedback systems, and asset tracking potential may be possible forapplications such as commercial truck fleets, airplanes, andmining/earthmover equipment.

In one exemplary embodiment of the present subject matter, a tireassembly with integrated power generation features includes a pneumatictire structure, a piezoelectric device, and an electronics assembly. Thepneumatic tire structure is characterized by a crown having a treadportion for making contact with a ground surface, bead portions forseating the tire to a wheel rim, and sidewall portions extending betweeneach bead portion and the crown. A carcass is provided within the tirebetween the bead portions across the sidewall portions and the crown, abelt package is provided within the tire crown between the tread portionand the carcass, and an inner liner forms an interior surface of thetire structure. The piezoelectric device is configured to generateelectric charge therein when the tire structure is subjected tomechanical strains. The electronics assembly is coupled to the powergeneration devices (in some embodiments via an energy storage device)such that selected components of the electronics assembly are powered byelectric charge generated by the piezoelectric device.

The piezoelectric device can be integrated at a variety of differentlocations associated with the pneumatic tire structure, including butnot limited to in the crown between the tread portion and the beltpackage, in the crown between the belt portion and the carcass, in thecrown between the carcass and the inner liner, in a sidewall between thecarcass and the tire exterior, in a sidewall between the carcass and theinner liner, and in the zone base near a selected bead portion of thetire structure. In some embodiments, the pneumatic tire structure alsoincludes a cap ply portion between the belt package and the treadportion. In such embodiments, the piezoelectric device may be embeddedin the tire crown either between the tread portion and the cap plyportion or between the belt package and the cap ply portion. In otherembodiments, the belt package includes at least first and second steelbelts and the piezoelectric device could be mounted between therespective steel belts. The piezoelectric device may also be attached toor embedded in a rubber casing which provides additional support for thepiezoelectric device. The rubber casing and piezoelectric device maythen be mounted to the inner liner or to the exterior tread portion ofthe pneumatic tire structure.

In another exemplary embodiment of the present technology, a tireassembly with integrated power generation features includes a pneumatictire structure, a safety support, a piezoelectric device, and anelectronics assembly. The pneumatic tire structure is characterized by acrown having a tread portion for making contact with a ground surface.The safety support is configured for mounting on a wheel rim inside ofthe pneumatic tire structure in order to support the tread portion inthe event of the loss of tire inflation. The safety support includes anannular body having an inner surface intended to fit around the wheelrim and an outer cap to be engaged by the tread portion of the tire inthe event of a loss of pressure. The piezoelectric device may beintegrated with a selected portion of the safety support and isconfigured to generate electric charge therein upon the safety supportbeing subjected to mechanical strains during loss of pressure to thepneumatic tire structure. The electronics assembly is coupled to thepiezoelectric device and selected components therein are powered by theelectric charge generated by the piezoelectric device. The electriccharge may also be used in some embodiments to trigger a signalindicating when the pneumatic tire structure is operating under loss oftire inflation.

A still further exemplary embodiment of the present technologycorresponds to a tire assembly including a non-pneumatic structurallysupported tire, a piezoelectric device and an electronics assembly. Thenon-pneumatic structurally supported tire includes a reinforced annularband, a plurality of web spokes extending transversely across andradially inward from the reinforced annular band, and a mounting band atthe radially inner end of the web spokes. A tread portion may also bedisposed on a radially outer extent of the reinforced annular band. Thepiezoelectric device may be integrated with the non-pneumaticstructurally supported tire in such exemplary locations as the interiorof the reinforced annular band or on one or more of the plurality of webspokes. Upon the non-pneumatic structurally supported tire beingsubjected to mechanical strains, the piezoelectric device generateselectric charge therein which is then used to power one or moreelectronic components of an electronics assembly.

In accordance with more particular embodiments of the presentlydisclosed technology, some embodiments of the aforementionedpiezoelectric device(s) may correspond to a fiber composite structurewith a plurality of piezoelectric fibers embedded in an epoxy matrix.The piezoelectric device(s) may alternatively include a piezoceramicwafer substantially surrounded by a protective casing and provided withembedded first and second electrical leads for connecting to thepiezoceramic wafer (e.g., via electrodes). In still further embodiments,the piezoelectric device(s) include a layer of piezoceramic materialwith respective conductive layers (e.g., aluminum or stainless steellayers) adhered to opposing sides thereof with a polyimide adhesive(e.g., a high temperature thermoplastic polyimide). Piezoelectricdevices may sometimes include multiple piezoelectric elements connectedtogether in series or parallel. Such multiple piezoelectric elements mayalso be configured with polarization directions that are either in-phaseor opposing, and with either d33 or d31 displacement modes. Thepiezoelectric elements may include such materials as lead zirconatetitanate (PZT), barium titanate, quartz, cadmium sulfide, polyvinylfluoride (PVF) and polyvinyl chloride (PVC).

Additional objects and advantages of the present subject matter are setforth in, or will be apparent to, those of ordinary skill in the artfrom the detailed description herein. Also, it should be furtherappreciated that modifications and variations to the specificallyillustrated, referred and discussed features and steps hereof may bepracticed in various embodiments and uses of the invention withoutdeparting from the spirit and scope of the subject matter. Variationsmay include, but are not limited to, substitution of equivalent means,features, or steps for those illustrated, referenced, or discussed, andthe functional, operational, or positional reversal of various parts,features, steps, or the like.

Still further, it is to be understood that different embodiments, aswell as different presently preferred embodiments, of the presentsubject matter may include various combinations or configurations ofpresently disclosed features, steps, or elements, or their equivalents(including combinations of features, parts, or steps or configurationsthereof not expressly shown in the figures or stated in the detaileddescription of such figures).

Additional embodiments of the present subject matter, not necessarilyexpressed in this summarized section, may include and incorporatevarious combinations of aspects of features, components, or stepsreferenced in the summarized objectives above, and/or other features,components, or steps as otherwise discussed in this application. Thoseof ordinary skill in the art will better appreciate the features andaspects of such embodiments, and others, upon review of the remainder ofthe specification.

BRIEF DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure of the present subject matter, includingthe best mode thereof, directed to one of ordinary skill in the art, isset forth in the specification, which makes reference to the appendedfigures, in which:

FIG. 1 displays a generally cross-sectional view of an exemplarypneumatic tire structure with integrated self-powered electroniccomponents in accordance with the present subject matter;

FIG. 2A displays a generally perspective view of a first exemplarypiezoelectric structure for use with a power generation device inaccordance with the present subject matter;

FIG. 2B displays a generally perspective view of a second exemplarypiezoelectric structure for use with a power generation device inaccordance with the present subject matter;

FIG. 2C displays a generally exploded perspective view of a thirdexemplary piezoelectric structure for use with a power generation devicein accordance with the present subject matter;

FIG. 3 provides a schematic representation of additional exemplaryaspects of a power generation device in accordance with the presentsubject matter, particularly regarding an exemplary power conditioningmodule;

FIG. 4A provides a block diagram representation of exemplary integratedself-powered electronics including a power generation device and a tireelectronics system and exemplary interaction thereof in accordance withthe present subject matter;

FIG. 4B provides a block diagram representation of exemplary integratedself-powered electronics including a power generation device and a tireelectronics system and alternative exemplary interaction thereof inaccordance with the present subject matter;

FIG. 5 provides a block diagram representation of an exemplary tireelectronics system in accordance with the disclosed technology;

FIG. 6 provides a block diagram representation of an exemplary remotereceiver configuration in accordance with the present subject matter;

FIGS. 7A, 7B, 7C and 7D illustrate respective exemplary configurationsof multiple piezoelectric elements in stacked combination for use in apower generation device in accordance with the present subject matter;

FIGS. 8A and 8B respectively illustrate exemplary configurations ofmultiple piezoelectric elements in series and parallel combination foruse in a power generation device in accordance with the present subjectmatter;

FIGS. 9A, 9B and 9C respectively illustrate exemplary configurations ofmultiple piezoelectric elements coupled to one or more energy storagedevices and one or more application electronics modules in accordancewith exemplary power generation device and tire electronics systemembodiments of the present technology;

FIG. 10 provides an axial half-sectional view of a tire having a safetysupport mounted on a wheel rim inside the tire and with integratedself-powered electronic components in accordance with the presentsubject matter;

FIG. 11 provides an axial half-sectional view of the tire and safetysupport of FIG. 10 in which the safety support is in the run-flatcondition; and

FIG. 12 provides a side plan view of an exemplary non-pneumaticstructurally supported tire with integrated self-powered electroniccomponents in accordance with the present subject matter.

Repeat use of reference characters throughout the present specificationand appended drawings is intended to represent same or analogousfeatures or elements of the invention. It should be appreciated thatvarious features illustrated in the appended drawings are notnecessarily drawn to scale, and thus relative relationships among thefeatures in such drawings should not be limiting the presently disclosedtechnology.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As discussed in the Summary of the Invention section, the presentsubject matter is particularly concerned with an improved system andmethod for powering electronic systems integrated within a tirestructure. A power generation device utilizes piezoelectric technologyto convert mechanical strain associated with tire flexure to electriccurrent that is then conditioned and stored in an energy storage device.Sufficient accumulations of such stored energy can then power electronicsystems, examples of which include components for identifying variousphysical tire parameters as well as radio frequency (RF) transmissiondevices.

A power generation device in accordance with the disclosed technologygenerally includes two exemplary components, a piezoelectric structureand a power conditioning module. Aspects of various exemplarypiezoelectric structures are described with reference to FIGS. 2A, 2Band 2C and an exemplary power conditioning module (with energy storagedevice) is presented in and discussed with reference to FIG. 3.Additional aspects related to exemplary configurations of one or morepiezoelectric elements in a power generation device are illustrated inFIGS. 7A-7D, respectively, and in FIGS. 8A and 8B. The output of thepower conditioning module may then preferably be used to powerelectronics systems within a tire or wheel assembly. An example of atire electronics system, including sensors, a microcontroller, and an RFtransmitter is presented in FIG. 5. Aspects of exemplary interactionbetween a power generation device and tire electronics system isdiscussed with reference to FIGS. 4A and 4B, respectively. Furtheraspects of exemplary interaction between multiple piezoelectric elementsand one or more tire electronics modules are represented in FIGS. 9A, 9Band 9C. Finally, an exemplary embodiment of a remote receiverconfiguration for obtaining information transmitted from a tireelectronics system is presented with respect to FIG. 6.

Selected combinations of the aforementioned aspects of the disclosedtechnology correspond to a plurality of different embodiments of thepresent subject matter. It should be noted that each of the exemplaryembodiments presented and discussed herein should not insinuatelimitations of the present subject matter. Features or steps illustratedor described as part of one embodiment may be used in combination withaspects of another embodiment to yield yet further embodiments.Additionally, certain features may be interchanged with similar devicesor features not expressly mentioned which perform the same or similarfunction. Similarly, certain process steps may be interchanged oremployed in combination with other steps to yield additional exemplaryembodiments of a method for generating electric power from a rotatingtire's mechanical energy.

Reference will now be made in detail to the presently preferredembodiments of the subject system and method of generating power forelectronics systems integrated within a tire or wheel assembly.Referring now to the drawings, FIG. 1 provides a generallycross-sectional view of an exemplary pneumatic tire assembly 10 withintegrated self-powered electronic components 12 in accordance with thepresent subject matter. A power generation device (PGD) 14 is preferablyprovided in conjunction with electronic components internal to a tirestructure 16 such that the electronics components are self-poweredwithin the tire assembly 10.

The capabilities of the subject power generation device withpiezoelectric materials, as hereafter presented, offer numerousadvantages over conventional techniques for providing power within atire assembly. Antenna beam power scavenging techniques, as previouslydiscussed, are no longer one of limited options to choose from forpowering tire electronics. As such, the functional capabilities of manytypes of tire electronics are generally increased. The option ofutilizing batteries for power generation is no longer essential, thusavoiding costly and cumbersome battery replacement. Although thepresently disclosed technology provides for a power generation devicethat enables antenna beam power and batteries to be eliminated, itshould be appreciated that a power generation device could employ ahybrid combination of piezoelectric technology and/or batteries and/orantenna beam scavenging to power different selected electroniccomponents within a wheel assembly.

A typical pneumatic tire structure 16 is characterized by a crown 15which supports an exterior tread portion 18 and sidewalls 20 that extendto bead portions 22. Sidewalls 20 generally extend between section lines17 and 19 and the tire crown 15 generally extends between the twosection lines 19. Tire beads 22 are generally provided such that thetire structure 16 can be effectively seated to the rim of a wheelassembly. An inner liner of air-impermeable material forms the interiorsurface of the tire, including interior crown surface 24 and interiorsidewall surfaces 26. A carcass 23 extends between beads 22 acrosssidewall portions 20 and crown 15, and under inflation pressure definesthe tire's shape and transmits forces for traction and steering. A beltpackage including at least first and second belts 21 a and 21 b (usuallyfashioned from a material such as steel) is provided within tirestructure 16 generally along the crown 15. In some tires, additionaloverlay layers, or cap plies, may be provided to generally cover thesteel belt and help keep the belt package from separating from the tire,thereby providing enhanced tire performance and durability. Cap plyportion 25 may include one or more layers of industrial textilereinforcement.

PGD 14, as illustrated in the exemplary tire assembly embodiment of FIG.1, may be mounted to the interior crown surface 24 of tire structure 16.This location is generally well-suited for actuation of thepiezoelectric device within PGD 14 as the exterior tread portion 18moves along a ground surface and results in flexure of the tirestructure 16. This tire flexure coupled with the general mechanicalvibrations as the tire assembly 10 moves along a surface enablepiezoelectric device within the power generation device 14 to generateelectric current, which is then conditioned and stored in an energystorage device for powering the tire electronics 12. Although theinterior crown surface 24 is a logical location for mounting powergeneration device 14, it should be appreciated that PGD 14 may also bemounted to other locations, including the interior sidewall surface 26.Such location may offer less strain on the piezoelectric elements withinthe subject PGD 14 while still providing enough power generation forcertain electronic applications.

Further, PGD 14 or at least the piezoelectric element portion of PGD 14could be cured within tire structure 16. Examples of locations where PGD14 or the piezoelectric element thereof may be embedded within tirestructure 16 include without limitation, in the tire crown or summitbetween tread portion 18 and the belt package embodied by exemplaryfirst and second steel belts 21 a and 21 b, in the summit between firstand second steel belts 21 a and 21 b, in the summit between theinnermost steel belt (e.g., belt 21 b in FIG. 1) and the inner carcass23, in the summit between the carcass 23 and the inner liner providedalong surfaces 24 and/or 26, in a sidewall between the carcass 23 andthe inner liner, in the sidewall between the carcass and sidewall rubbergenerally provided at locations 27, or embedded at locations 29 oftenreferred to as the tire zone base. For tires that include cap plies suchas cap ply portion 25, additional particular locations where PGD 14 orthe corresponding piezoelectric element may be embedded include in thetire summit between the tread portion 18 and the cap ply portion 25 orbetween the cap ply portion 25 and the belt package embodied by firstand second steel belts 21 a, 21 b.

PGD 14 or selected elements thereof may alternatively be provided in anadditional rubber or elastomer casing before being adhered to orembedded in the tire to provide additional protection. Such casingadditionally provides for facilitated adhesion of the PGD to a tirestructure. The rubber casing may alternatively be provided adjacent to asingle side of PGD 14 or selected elements thereof for support, whichmay then be adhered to an inner surface of a tire structure. In otherembodiments, PGD 14 may additionally be mounted to a relatively rigidsubstrate such as one made of fiberglass or other substantially rigidmaterial to provide additional protection and support for suchstructure. The rubber casing and/or substrate and/or other elements thatare provided adjacent to PGD 14 collectively serve as a mechanicalinterface between the rather rigid piezoelectric element within PGD 14and the rather flexible material of the tire structure 16 in which suchelements are incorporated. Provision of such a mechanical interfacehelps to protect tire structure 16 from damage that might be caused bythe presence of the often unyielding piezoelectric element and alsoprotects the piezoelectric element from the relatively extreme shapedistortions that the tire would otherwise impose on the piezoelectricelement. In some embodiments, a mechanical optimization may be performedwith respect to the intermediate layer to control the ratio of stresses(forces) and strains (displacements) that occur on either side of theinterface.

Exemplary locations for integration of such a patch and piezoelectricelement combination include along the inner liner provided alongsurfaces 24 and/or 26 or at the exterior of the tire structure 16. Inaccordance with the variety of possible locations for PGD 14, it shouldbe understood that the term “integrated” generally encompasses allpossible locations, including being mounted on or in a tire structure.

The subject piezoelectric technology may also be utilized innon-conventional tires, in other words, tires having variations to theexemplary structure illustrated in FIG. 1. In one example, the powergeneration technology disclosed herein may be incorporated into tireshaving safety support features mounted inside their tires on their wheelrims in order to take up load in the event of tire failure, thussupporting the tread strip of the tire in the event of a loss ofinflation pressure. FIGS. 10 and 11 are now discussed to illustrateaspects of such a tire with safety support features. FIG. 10 provides anaxial half-sectional view of a safety support 150 mounted around apreferential wheel rim 152 and inside the cavity 154 of a correspondingtire 156. The tire 156 is designed to be mounted on the wheel rim 152and in particular has two beads of different diameters. The support 150has three main parts: a base 158 of annular overall shape and reinforcedwith a ply 160 oriented longitudinally at substantially zero degrees, asubstantially annular cap 162 with longitudinal grooves 164 in itsradially outer wall, and an annular body 166 for joining the base 158and the cap 162 together. The cavity defined by portion 168 makes itpossible to reduce the weight of support 150 as well as provide inconjunction with the other portions of support 150 to give uniformsupport under run-flat conditions (i.e., under full or partial loss oftire pressure). FIG. 11 shows a safety support similar to that of FIG.10 while it is in operation along a ground surface, e.g., during arun-flat condition. The cap 162 of the support 150 is in contact withthe radially inner surface of the cap of the tire 156, thus preventingthe tire 156 from riding on the wheel rim 152 during loss of airpressure in tire cavity 154. Additional details of such a tire withsafety support are disclosed in U.S. Pat. No. 5,891,279 (Lacour), whichis incorporated by reference herein for all purposes. It should beappreciated that other specific safety supports may be integrated withina tire structure. Although the support disclosed in Lacour is agenerally solid circular device, other support embodiments could be madeof other support materials (e.g., foam rubber, that undergoesdeformation when the tire is in a run-flat mode.

Referring still to FIGS. 10 and 11, a piezoelectric element or otherselect portions of PGD 14 may be integrated with the safety support 150of such exemplary run-flat tire structures. For example, PGD 14 orportions thereof may be integrated with the cap portion of safetysupport 150, for example between one of the grooves 164. An alternativemounting location may correspond to an inner surface of the area definedby cavity 168. It should be appreciated that PGD 14 or specifically thepiezoelectric element thereof may be mounted on, attached to or embeddedin still further locations relative to a tire having a safety supportfeature for facilitating run-flat operation while remaining with thespirit and scope of the present invention.

When a tire such as described with respect to FIGS. 10 and 11 isoperating under normal inflation pressures, the tire 156 undergoesdeformations, but the safety support 150 does not. However, when thetire is operating in a run-flat mode (also referred to as extendedmobility mode) the safety support 150 does undergo deformation. Thestrains induced by these deformations cause a piezoelectric elementintegrated with safety support 150 to generate electrical energy. Thisgeneration of electrical energy can be used to trigger a visible and/oraudible indicator, alarm, or other signaling mechanism to indicate tothe vehicle driver that the tire is operating in a “run flat” mode withfull or partial loss of pressure in at least one tire. The generatedelectrical energy can also be used to power electronic devices withinthe tire/wheel assembly. Electronic devices can be used to perform suchexemplary functions as counting the number of tire revolutions orduration in units of miles, kilometers, etc. that the tire with safetysupport has traveled while operating in a run-flat or extended mobilitymode, measuring the contact patch length of the safety support as anindicator of how severely the tire is under-inflated, and measuring thetemperature of the safety support while in extended mobility mode. Aselect combination of the above exemplary data may be used to determinethe effective useful life remaining for the safety support. Theremaining effective usage of the safety support and other related data,including information indicating when the tire was operated under lossof tire pressure, may be stored in an interfaced memory device fixedonto or into the tire safety support. When the tire is serviced, atechnician can then determine if the support insert also requiresreplacing. In some embodiments, enough electrical energy may beaccumulated to transmit a wireless signal to a central vehicle locationto warn the driver when an alert condition exists.

Yet another example of a tire with which the subject piezoelectrictechnology may be utilized is a structural supported tire different thanthat described with reference to FIGS. 10 and 11. A non-pneumaticstructurally supported tire will now be briefly described with referenceto FIG. 12. The non-pneumatic tire 170 of FIG. 12 is designed to supporta load solely with its structural components and, contrary to themechanism of conventional pneumatic tires, without support from internalair pressure. Structurally supported non-pneumatic tire 170 has a groundcontacting tread portion 172, a reinforced annular band 174 disposedradially inward of the tread portion, a plurality of web spokes 176extending transversely across and radially inward from the annular band,and a mounting band 178 at the radially inner end of the web spokes. Themounting band 178 anchors the tire 170 to a wheel 180 or hub. Althoughnot illustrated in FIG. 12, an additional plurality of web spokes mayextend in the equatorial plane. The reinforced annular band 174 may moreparticularly include an elastomeric shear layer, a first membraneadhered to the radially innermost extent of the elastomeric shear layer,and a second membrane adhered to the radially outermost extent of theelastomeric shear layer. The membranes have a tensile stiffness that isgreater than the shear stiffness of the shear layer so that thereinforced annular band undergoes shear deformation under load. Thereinforced annular band 174 supports loads on the tire. As indicated inFIG. 12, a load L placed on the tire axis of rotation X is transmittedby tension in the web spokes 176 to the annular band 174. The annularband 174 acts in a manner similar to an arch and provides acircumferential compression stiffness and a longitudinal bendingstiffness in the tire equatorial plane sufficiently high to act as aload-supporting member. Under load, the annular band deforms in contactarea C with the ground surface through a mechanism including sheardeformation of the band. The ability to deform with shear provides acompliant ground contact area C that acts similar to that of a pneumatictire, with similar advantageous results. Additional details of astructurally supported non-pneumatic tire such as illustrated withrespect to FIG. 12 are disclosed in U.S. Patent Application Publication2004/0159385, which is incorporated herein by reference for allpurposes.

Referring still to FIG. 12, a piezoelectric element or other selectportions of PGD 14 may be integrated with the structurally supportednon-pneumatic tire 170. For example, PGD 14 or portions thereof may beintegrated at the interior of the ground-contacting tread portion 172,at the interior of the reinforced annular band 174, or on one or more ofthe web spokes 150. It should be appreciated that PGD 14 or specificallythe piezoelectric element thereof may be mounted on, attached to orembedded in still further locations relative to a structurally supportednon-pneumatic tire while remaining with the spirit and scope of thepresent invention.

When a tire such as described with respect to FIG. 12 rotates along aground surface, it undergoes deformations. The strains induced by thesedeformations cause a piezoelectric element integrated with non-pneumatictire 170 to generate electrical energy. This electrical energy can thenby used to power electronic devices within the tire/wheel assembly.Electronic devices can be used to perform such exemplary functions ascounting the number of tire revolutions or duration in units of miles,kilometers, etc. that the non-pneumatic tire has traveled, measuring thecontact patch length of the non-pneumatic tire as an indicator of howseverely the tire is loaded, and measuring the temperature of thenon-pneumatic tire. A select combination of the above exemplary data maybe used to determine the effective useful life remaining for thenon-pneumatic tire. The remaining effective usage of the tire and otherrelated data may be stored in an interfaced memory device fixed onto orinto the tire. In some embodiments, enough electrical energy may beaccumulated to transmit a wireless signal to a central vehicle locationto warn the driver when an alert condition exists.

PGD 14 generally comprises two main components, a piezoelectric deviceand a power conditioning module. The piezoelectric device is subjectedto mechanical strains caused by tire rotation, thereby generating chargein one or more piezoelectric elements (as should be understood by one ofordinary skill in the related art). This electric charge is thenpreferably provided to a power conditioning module where the resultingcurrent is rectified, conditioned, and stored for use with powerelectronics.

The piezoelectric device could comprise a variety of piezoelectricmaterials, including but not limited to barium titanate, polyvinylidenefluoride (PVDF), lead zirconate titanate (PZT) crystals, or PZT fibers.A particular type of piezoelectric material that may be utilized inaccordance with the subject power generation device is a piezoelectricfiber composite structure, such as those disclosed in U.S. Pat. Nos.5,869,189 and 6,048,622 issued to Hagood, IV et al., hereby incorporatedby reference for all purposes. A similar example of such Active FiberComposites (AFCs) that may be utilized in accordance with the presentsubject matter corresponds to “PiezoFlex” brand technology, such asoffered for sale by Continuum Control Corporation.

FIG. 2A displays an isometric view of a piezoelectric AFC structure 28in accordance with exemplary aspects of the presently disclosed powergeneration device. Such a piezoelectric AFC structure 28 includes aplurality of piezoelectric fibers 30 that are unidirectionally alignedto provide actuation and stiffness of AFC structure 28. The fibers 30are surrounded by a resin matrix 32 of epoxy or polymer, that provides adamage tolerance through load transfer mechanisms. The piezoelectricfibers have a common poling direction 34 transverse to theirsubstantially co-parallel axial arrangement.

Electrode layers are preferably provided on separate substrates alongtwo opposing surfaces of the fiber/resin matrix configuration to provideelectrical input and output to the AFC structure 28. In accordance withthe exemplary embodiment of FIG. 2A, electrode layers 36 are configuredwith an interdigital arrangement with alternating finger-to-fingerpolarity. Such interdigitated electrode layers 36 may be etched ontoseparate substrate layers (of polyimide or polyester, for example) usingscreen-printing techniques as known in the art and conductive ink suchas silver-loaded epoxy. The alignment of the interdigital electrodeconfiguration of FIG. 2A is designed to enhance the directionality ofthe electromechanical response of the AFC structure 28, as well asprovide for relatively high charge and coupling coefficients. The amountof resin matrix 32 between electrodes 36 and fibers 30 is preferablyminimized to achieve greater performance capabilities.

The orientation of the fibers in an AFC structure relative to a tirestructure is a particular design factor in accordance with the subjecttechnology. When orienting the fibers along the circumferentialdirection of a tire, piezoelectric fibers are subjected to generallyhigh tensile strains, but low compressive strains. Orienting the fiberdirection along the radial direction of a tire couples the primaryenergy harvesting to the radial strains. This orientation is less likelyto cause damage to fibers, but yields a potentially highersusceptibility of compressive depoling of the fibers. Thus, orienting apiezoelectric patch of a power generation device of the present subjectmatter radially versus circumferentially along the summit of a tirestructure may be determined based on the size of the patch and thespecific tire environment to which it will be subjected. Moreparticularly, optimal placement and orientation of a piezoelectric AFCstructure may be based on factors such as maximum power desired per tirecycle, peak tensile and compressive strains along radial versuscircumferential mounting directions, and strain uniformity over an AFCstructure at given times.

More specific characteristics of a piezoelectric AFC structure, such asthe exemplary embodiment of FIG. 2A, can be tailored for differentapplications. For instance, the piezoelectric fibers may correspond to avariety of different PZT materials, including PZT 5A, PZT 5H, PZT 4, PZT8, and PMN-33PT. Another specific design constraint corresponds to thediameter 38 of the piezoelectric fibers, which may typically be in arange from about three thousandths of an inch (mils) to about fifteenmils. Other specific dimensions that may be designed for particularapplications include the width 40 and pitch 42 of the electrode fingersin interdigital layers 36. An example of electrode finger width 40corresponds to about twenty-five mils, and an exemplary range forelectrode pitch 42 corresponds to from about twenty mils to aboutone-hundred mils. A specific example of an overall piezoelectric AFCstructure for use in accordance with the present subject mattercomprises interdigital electrodes with a forty-five mil electrode fingerpitch and PZT-5A piezoelectric fibers with a ten mil diameter.

Additional design constraints of a piezoelectric structure for use in apower generation device in accordance with the present subject mattermay be considered for certain applications. For instance, there may becertain design constraints relative to the size and processingcapabilities of a piezoelectric patch for integration within a tirestructure. Assume that a PGD in accordance with the disclosed technologycomprises a piezoelectric device mounted circumferentially along a tiresummit along with an integrated power conditioning module. The PGD ispreferably provided in an additional rubber or elastomer casing orsupported on a rubber, fiberglass, or other supportive substrate when itis adhered to the tire interior to provide it with additionalprotection. A rubber casing or substrate additionally provides forfacilitated adhesion of the PGD to a tire structure.

In accordance with such exemplary PGD configurations as mentioned above,there is generally no length constraint of the piezoelectric patch;however, testing has shown that patches over seventy mm in length tendto fail. A maximum width of about eighty mm may be desired for certainapplications. A maximum thickness of the piezoelectric patch (without apower conditioning module) may be about seven-hundred micrometers, and amaximum mass of about twenty grams (including a piezoelectric patch anda power conditioning module) may be desired for certain applications. Inorder for the piezoelectric patch to be bonded to a rubber patch foradhering to a tire interior, the patch must generally be able to surviveabout one-hundred-seventy degrees Celsius for about thirty minutes whilesubjected to about twenty bar pressure and also to survive aboutone-hundred-fifty degrees Celsius for about sixty minutes at abouttwenty bar pressure. It should be appreciated that these specificconstraints may change with the advancement of pertinent materials andadhesion technologies. In addition, a PGD in accordance with the presentsubject matter should preferably be able to withstand operatingconditions from about negative forty degrees Celsius to aboutone-hundred-twenty-five degrees Celsius, a maximum tire speed of aboutone-hundred-sixty kph, and an endurance of either about ten years orseven-hundred-thousand miles.

Yet another type of piezoelectric patch that may be utilized in PGD 14in accordance with some embodiments of the present invention correspondsto generally solid piezoeceramic wafers. Such piezoceramic wafers may besingle-crystal or polycrystalline structures, including but not limitedto wafers made of polycrystalline ferroelectric materials such as bariumtitanate (BaTiO₃) and lead zirconate titanate (PZT).

Referring now to FIG. 2B, a more particular example of a potentialpiezoelectric device 28′ for use in a power generation device 14 of thepresently disclosed technology is illustrated. Piezoelectric device 28′corresponds to one or more piezoceramic wafers provided in one of aunimorph, bimorph or stacked/sandwich arrangement and packaged within aprotective skin 108. A unimorph arrangement generally corresponds to asingle modular portion (i.e., layer) of piezoceramic material, which maybe bonded to an inactive substrate in some embodiments. A bimorpharrangement generally corresponds to two modular portions (i.e., layers)of piezoceramic material that are bonded to opposing sides of a centermetallic shim layer, and a stacked, or sandwich, arrangement correspondsto several piezoelectric elements provided adjacent to and coupled withone another. Bimorph and stacked arrangements may yield a higher levelof generated charge versus amount of mechanical displacement thanunimorph arrangements for certain applications.

Referring still to FIG. 2B, the protective casing 108 in which one ormore piezoceramic wafers may be provided may serve as electricalinsulation for the piezoceramic wafers as well as a defense againsthumidity and potentially harsh contaminants. In some embodiments, thepiezoceramic wafers may comprise specific PZT materials such as PZT-5Aand/or PZT-5H. Distributed electrodes 110 may be made of such materialsuch as nickel and may be provided on top and bottom surfaces of theassembly for coupling to pre-attached first and second electrical leads112 and 114, respectively. Pins for connecting to leads 112 and 114 maybe accessible via a connector element 120 for a reliable component withno soldered wires. Additional pins at connector element 120 may providerespective electrical connections 116 and 118 for poling thepiezoceramic element(s) within piezoelectric device 28′. A specificexample of the type of piezoelectric device represented in FIG. 2B andthat may be utilized in accordance with the present subject mattercorresponds to “QuickPack” brand technology (e.g., ACXQuickPack-PowerAct QP15W), such as offered for sale by Mide TechnologyCorporation.

A still further example of a piezoelectric device for use in a powergeneration device in accordance with the present subject matter isrepresented in FIG. 2C as element 28″. FIG. 2C depicts a generallyexploded perspective view of a piezoelectric element 28″, includingmultiple layers provided in a generally stacked arrangement in whichindividual materials are layered on top of one another. A first layer inthe layered composite comprising piezoelectric element 28″ correspondsto a metal substrate layer 120, for example but not limited to a layerof stainless steel. Subsequent adhesive layers 122 are provided aroundan internal layer 124 of piezoelectric material. Piezoelectric layer 124may correspond in some embodiments to a piezoceramic material such asPZT. Adhesive layers 122 may in some embodiments comprise a polyimidematerial or more specifically a high temperature thermoplastic polyimide(e.g., LaRC™-SI brand material such as developed by NASA's LangleyResearch Center). A top layer 126 of piezoelectric element 28″ comprisesa metallic material such as but not limited to aluminum. Such multiplelayers may be combined together by placing the entire assembly in anautoclave in which the multiple layers are heated, squeezed together,allowed to cook, and then cooled to around room temperature. As thepiezoelectric element 28′ begins to cool, the substrate layer 120 whichis bonded to piezoceramic layer 124 acts to keep piezoceramic layer 124in compression while is itself in a continuous state of tension. Thisinduced pre-stress may cause the piezoelectric device to be ultimatelyformed in a slightly curved configuration, and allows the finisheddevice to be subjected to much higher levels of mechanical deflectionthan some conventional piezoelectric devices without cracking.

A specific example of the type of piezoelectric device represented inFIG. 2C and that may be utilized in accordance with the present subjectmatter corresponds to “THUNDER” brand technology (e.g., Face ThunderActuator 6R), such as offered for sale by Face InternationalCorporation. THUNDER products generally correspond to Thin LayerUnimorph Ferroelectric Driver and Sensor devices that are made ofmultiple layers of material held together in a “sandwich-like” packagewith high strength bonding materials configured to provide internalpre-stresses. The adhesive layers 122 of piezoelectric element 28″ holdthe various device layers together despite relatively high internalstresses that are created during device manufacturing.

It should be appreciated that variations to the exemplary piezoelectricdevices discussed above for incorporation with a power generation deviceof the present subject matter as appreciated by one of ordinary skill inthe art may be implemented, and that such variations are within thespirit and scope of the present invention. For example, although thepiezoelectric elements presented herein are generally rectangular inshape, it should be appreciated that piezoelectric elements of differentshapes such as circular, square or otherwise may also be utilized.Additional modifications to the geometry, dimensions, material type,etc. of the piezoelectric elements are generally considered within thepurview of one of ordinary skill in the art.

Still further design aspects that may be implemented in accordance withthe present technology concern combination of multiple piezoelectricelements, such as now discussed with reference to FIGS. 7A-7D and 8A-8Brespectively. FIGS. 7A-7D illustrate respective exemplary configurationsof how multiple elements 130 may be stacked vertically inside a tirePGD. Although only two piezoelectric elements 130 are illustrated ineach configuration of FIGS. 7A-7D, it should be appreciated that morethan two piezoelectric elements may be utilized. Pieozoelectric elements130 may correspond to single-crystal or polycrystalline piezoceramicwafers, including but not limited to wafers made of polycrystallineferroelectric materials such as barium titanate (BaTiO₃) and leadzirconate titanate (PZT). Although not illustrated in FIGS. 7A-7D, itshould be appreciated that a center conductive shim layer may beprovided in between each adjacent piezoelectric element 130, such ascharacteristic of some bimorph and stacked piezoelectric arrangements.

The various configurations depicted in FIGS. 7A-7D illustrate differentpoling and displacement modes for the combined piezoelectric elements130. Shorter arrows 132 and 134 within each piezoelectric element 130represent the poling direction in each piezoelectric element, generallypointing from the positive to the negative poling electrode to which ahigh DC voltage would have been applied during manufacture of suchpieozelectric elements 130. Although not limited to the exemplary polingconfigurations shown in FIGS. 7A-7D, all such piezoelectric elements 130are characterized by polarization vectors 132 and 134 that are generallyparallel to the reference 3-axis. FIGS. 7B and 7D respectivelyillustrate configurations with both piezoelectric elements 130 havingpolarization vectors that are in-phase, while FIGS. 7A and 7Drespectively illustrate configurations with both piezoelectric elements130 having polarization vectors that are opposing, or out of phase. Thepiezoelectric configurations of FIGS. 7A and 7B are both in d33 mode,wherein displacement forces (represented by arrows 136) correspond to anexpansion in the same direction as the electrical field and the polingdirection. The piezoelectric configurations of FIGS. 7C and 7D are bothin d31 mode, wherein displacement forces (represented by arrows 138)correspond to a contraction perpendicular to the electrical field andthe poling direction.

The configurations of FIGS. 7A-7D illustrate respective examples of howmore piezoelectric material can be provided in a given strain field withthe same footprint as a single piezoelectric element. Such anarrangement has the potential to yield more energy output for eachrotation of a tire or wheel assembly, as the piezoelectric element(s)pass through the contact patch thereof.

Referring now to FIGS. 8A and 8B, it should be appreciated thatpiezoelectric elements 140 can be electrically connected in series (suchas depicted in FIG. 8A), in parallel (as depicted in FIG. 8B), or insome combination thereof when more than two piezoelectric elements arecombined. A series connection among piezoelectric elements 140 providesa generally higher voltage and lower current output than a singlepiezoelectric element. Such a configuration, as represented in FIG. 8A,may be especially useful for sensing applications, such as detection oftire revolutions as a piezoelectric element passes through the contactpatch of a tire or wheel assembly. A parallel connection amongpiezoelectric elements 140 provides a generally lower voltage and highercurrent output, which may be especially useful in energy harvestingapplications. Such a configuration, as represented in FIG. 8B, helps toreduce energy leakages and may simplify power conditioning electronics.Piezoelectric elements 140 may correspond to such specific piezoelectricelements 28, 28′ and 28″ as illustrated and discussed with reference toFIGS. 2A, 2B and 2C, respectively, or in other embodiments aspiezoceramic wafers such as elements 130 depicted in FIGS. 7A-7D,respectively.

The second main component of PGD 14, in addition to a piezoelectricelement is a power conditioning module, an exemplary embodiment of whichis represented in FIG. 3. The major functionality of a powerconditioning module in accordance with the present subject matter is torectify, condition and store the electric charge that is generated inthe piezoelectric structure 140. In general, power conditioning modulesmay be particularly designed for different electronics applications forwhich power is harvested. In accordance with an exemplary embodiment ofa tire monitoring system as disclosed in the present specification, theexemplary power conditioning module of FIG. 3 is designed according tocertain dynamic energy requirements. In particular, the exemplary powerconditioning module of FIG. 3 is designed such that the voltage output44 is generally about five volts, the maximum ripple of output voltage44 is within 35 ten mvolts, the minimum duty cycle of output voltage 44is about sixty seconds, and the maximum duty cycle of output voltage 44is about five seconds. Additional design requirements within which theexemplary power conditioning module embodiment of FIG. 3 operatescorrespond to a maximum energy requirement into an electronics system ofabout four mJoules and a time duration for which an electronics systemcan operate between about twenty-five msec and about two-hundred msec,depending on the functionality of the electronics system.

With further reference to the exemplary power conditioning module ofFIG. 3, one or more piezoelectric elements 140 are connected in parallelwith a rectifier, for example full-bridge rectifier 46. Alternativerectifier configurations could correspond to a doubling rectifier or anN-stage voltage multiplier. The rectified signal from rectifier 46 isthen stored in electrolytic capacitor 48. A specific example of anelectrolytic capacitor 48 suitable for employment in the exemplary powerconditioning module of FIG. 3 corresponds to a Panasonic TEL seriestantalum capacitor with a capacitance of about forty-seven μFarads.Other specific electrolytic capacitors may similarly be suitable forutilization as a storage element in accordance with the disclosed powerconditioning module. Other energy storage elements, such as rechargeablebatteries or super capacitors, may provide a suitable alternative incertain applications as an energy storage device for a powerconditioning module.

Once a sufficient amount of energy has accumulated in electrolyticcapacitor 48 (or other suitable energy storage device), a DMOS FETtransistor 54 acts as a switch to release the stored energy in capacitor48 to a voltage regulator 52. An example of a voltage regulator suitablefor use in the exemplary embodiment of FIG. 3 is a dual-mode five-voltprogrammable micropower voltage regulator such as the MAX666 brandoffered for sale by Maxim Integrated Products. Such a voltage regulatoris ideally suited for electronics systems that may typically have beenbattery-powered systems, and effectively convert the voltage acrosscapacitor 48 to a regulated five volt output voltage 44. A bipolar PNPtransistor 50 and zener diode 56 are additionally provided in theexemplary power conditioning module of FIG. 3.

Initially, transistors 50 and 54 are off, and the ground at the drain oftransistor 54 is floating such that no output voltage 44 is provided. Ascapacitor 48 charges to a sufficient voltage level (determined by zenerdiode 56 and the base-emitter junction of transistor 50), transistor 50turns on, activating transistor 54 and latching transistor 50. At thispoint, capacitor 48 is allowed to discharge through the circuitryproviding a five volt regulated output 44 to an electronics system.Typically, when the application electronics to which output voltage 44is supplied has finished its useful work, the electronics system sends asignal back at signal path 58, through resistor 60 and capacitor 62 toturn off PNP transistor 50 and deactivate FET 54 such that energy canonce again begin to accumulate on capacitor 48.

Energy that is generated by PGD 14 may be applied to a variety ofdifferent tire electronics systems (TESs) in accordance with the presentsubject matter. FIGS. 4A and 4B, respectively, illustrate exemplaryaspects of interaction between a PGD 14 and TES 12.

In accordance with FIG. 4A, energy is allowed to accumulate on an energystorage device in the PGD (for example, capacitor 48) until a sufficientcharge has been obtained to perform the desired functions in TES 12.Between power cycles, TES 12 remains unpowered, and thus the activationof TES 12 is governed by the rate at which energy is accumulated in theenergy storage device of PGD 14. When sufficient energy is accumulatedin PGD 14, a supply voltage “V_(dd)” and ground voltage “V_(SS)” will beprovided at paths 64 and 66 respectively to TES 12. TES 12 will returnan “Active” signal along path 58 indicating electronics in TES 12 arecurrently functioning. When the given electronics in TES 12 are donewith their respective tasks, then the “Active” signal goes low and theenergy storage device in PGD 14 once again accumulates energy. Thiscycle will repeat as long as a tire assembly rotates at or above a giventhreshold speed, which may generally be about twenty kph.

In accordance with the exemplary interaction presented and discussedwith reference to FIG. 4B, PGD 14 continuously provides voltage “V_(dd)”and ground “V_(ss)” signals to TES 12 along with a “Fuel Gage” signalrepresentative of the amount of energy stored in PGD 14. When power isapplied to TES 12, a microprocessor or other suitable electroniccomponent can periodically activate itself and monitor the Fuel Gagesignal from PGD 14. If a sufficient amount of energy is available in theenergy storage device of PGD 14, then TES 12 will engage in a specifiedtask. If a sufficient amount of energy is not available, then TES 12will go into a low power mode where it consumes less than about one μAof power. The Fuel Gage signal is thereafter periodically checked untilenergy accumulation is sufficient. This cycle of waiting for sufficientenergy accumulation, engaging in a specified task, and returning to lowpower mode is preferably repeated in a continuous fashion as long as thetire is rotating at or above a given threshold speed.

As previously mentioned, TES 12 could comprise a variety of differentelectronic applications depending on what sort of components areincluded in a tire or wheel assembly. A specific example of a tireelectronic system 12 corresponds to a tire monitoring system, such ashereafter discussed with reference to FIG. 5. In particular, the tiremonitoring system of FIG. 5 measures temperature and pressure within atire structure and sends the results by means of a radio frequency (RF)transmitter 68 to a remote receiver location. An example of respectivetransmitter and receiver modules for utilization with aspects of thedisclosed technology corresponds to respective TX2 and RX2 brand UHF FMData Transmitter and Receiver Modules such as offered for sale byRadiometrix Ltd.

A five-volt power signal “V_(dd)”, ground signal “V_(ss)”, and either an“Active” or “Fuel Gage” signal as discussed with reference to FIGS. 4Aand 4B are preferably provided from PGD 14 to a microcontroller 70. Anexample of a suitable microcontroller for use with the disclosedtechnology is a Microchip brand PIC16LF876 28-pin CMOS RISCmicrocontroller. Microcontroller 70 is activated when power is appliedat input path 64 and then applies power to both temperature sensor 72and pressure sensor 74 (as well as any additional sensors or appropriateelectronic devices in TES 12). An example of a temperature sensor 72suitable for utilization with the disclosed technology is a LM50 SOT-23Single-Supply Centigrade Temperature Sensor such as offered for sale byNational Semiconductor. An example of a pressure sensor 74 suitable forutilization with the disclosed technology is a Model 1471 PC BoardMountable Pressure Sensor such as offered for sale by ICSensors andMeasurement Specialties Inc. Additional sensors 76, 78 and 80,respectively, may measure additional characteristics of a tire structureor corresponding wheel assembly.

Yet another component of the exemplary TES embodiment 12 of FIG. 5corresponds to a rechargeable battery 81 that may also be configured toreceive electric charge generated within piezoelectric structure 28 ofPGD 14 and to store additional energy for the integrated tireelectronics. Energy stored in battery 81 can typically be stored for amuch longer period of time than in other storage devices such asexemplary capacitor 48. Energy stored in battery 81 can be provided tomicrocontroller 70 when not enough power is generated by actuation ofthe piezoelectric device. Such a situation could occur, for instance,when the vehicle is stationary or when the tires are removed from avehicle. For example, stored energy may be needed to power TES 12 when aground crew checks the air pressure in stationary tires on a commercialairliner. Also, battery 81 may serve to provide power to TES 12 suchthat information for managing tire inventories or retreads is availablewhen a tire is removed from the vehicle.

With further reference to the exemplary TES embodiment 12 of FIG. 5,microcontroller 70 preferably includes an analog-to-digital (A/D)converter that receives information from sensors 72 through 80,respectively, and converts it to digital information. Microcontroller 70also comprises memory, preferably non-volatile EEPROM, which stores aunique identification tag that provides sufficient information toidentify the tire or wheel assembly. Such an identification variable maybe especially useful in tracking tires and vehicles in commercialapplications such as trucking fleets, airplanes, etc. Once the desiredinformation, such as that provided by sensors 72 through 80respectively, is acquired by microcontroller 70 and converted to digitalinformation, microcontroller 70 preferably shuts off power to thesensors and turns on power to RF transmitter 68 at lines 82 and 84respectively. The desired digitized information is then output on dataline 86 to RF transmitter 68, where the data is modulated onto an FMcarrier signal and transmitted via antenna 88 to a remote receiverlocation.

A vehicle employing tire assemblies with self-powered electronics inaccordance with the present subject matter are preferably equipped witha single receiver for obtaining the wirelessly transmitted informationfrom each tire assembly. FIG. 6 provides a block diagram representationof an exemplary remote receiver configuration 90 in accordance with thepresent subject matter. Receiver antenna 92 facilitates receipt ofinformation transmitted from each wheel assembly and relays theinformation to RF receiver 94, where the received information isdemodulated from its carrier signal and provided on path 96 to signalprocessor 98. A carrier detection signal is also provided from RFreceiver 94 to signal processor 98 via signal path 100. The dataoutputted from RF receiver 94 and the carrier detection signal arepreferably multiplied together in signal processor 98 such that a signalwithout spurious noise is obtained. This data signal with reduced errorprobability is then preferably routed to a driver circuit that convertsthe digital signal to a signal with voltage levels suitable fortransmission via an RS232 interface 102 to a host computer 104. Terminalemulation software is preferably provided at host computer 104 such thatthe data received via RS232 interface 102 is converted to informationreadily usable by an end user, such as that provided on a readabledisplay module.

It should be appreciated in accordance with the disclosed technologythat other electronic devices other than those specifically disclosed inthe present specification may be utilized with the subject powergeneration technology. For instance, it may be desired to transmit othertypes of information other than temperature, pressure and identificationto a remote location. Examples include the number of tire revolutions,amount of tire deflection, and vehicle speed. U.S. Pat. No. 5,749,984discloses other aspects of a tire monitoring system that may be employedwith the present subject matter, and such patent is hereby incorporatedby reference for all purposes. A tire electronics system may be coupledwith a global positioning system (GPS) to pinpoint a vehicle's preciselocation. A piezoelectric PGD may alternatively be utilized to powerlight assemblies or feedback systems in a wheel assembly. The number ofelectronics applications capable of being powered in accordance withaspects of the disclosed technology are vastly numerous and should in noway be limiting to the present subject matter.

It should be further appreciated in accordance with the presentlydisclosed technology that embodiments of the subject system and methodfor generating electric power are not limited to one power generationdevice and one tire electronics module per tire or wheel assembly. Theselective combination of multiple elements as disclosed herein shouldnot be limiting to the spirit and scope of the present invention.Referring now to FIGS. 9A, 9B and 9C, different exemplary combinationsof features are presented for potential incorporation within a tire,such as depicted in FIG. 1, or corresponding wheel assembly.

Referring now to FIGS. 9A, 9B and 9C, multiple piezoelectric elements140 may be provided within a tire or wheel assembly. Such piezoelectricelements 140 may be positioned in close proximity to one another withina tire or wheel assembly or may be distributed at different locationsthroughout the tire or wheel assembly. Piezoelectric elements 140 may insome embodiments comprise such specific exemplary piezoelectric elements28, 28′ and 28″ as illustrated and discussed with reference to FIGS. 2A,2B and 2C, respectively, or in other embodiments may comprisepiezoceramic wafers such as elements 130 depicted in FIGS. 7A-7D,respectively. Each piezoelectric element 140 of FIG. 9A generates energywhen passed through the contact patch of the tire or wheel assembly towhich it is mounted.

Referring particularly to FIG. 9A, the piezoelectric elements 140 may beelectrically connected in series or in parallel and are all coupled to acentral energy storage module 142. Energy storage module 142 includesselected power conditioning circuitry, such as described in the exampleof FIG. 3, including an energy storage device such as a capacitor orbattery for storing the energy generated by respective piezoelectricelements 140. The single energy storage module 142 is further coupled toan electronics module such as TES 12, such that selected applicationelectronics within TES 12 may receive power stored by energy storagemodule 142.

Referring particularly to FIGS. 9B and 9C, the distributed piezoelectricelements 140 may be electrically connected in series or in parallel andare each respectively coupled to distinct local energy storage modules142. Each energy storage module 142 includes selected power conditioningcircuitry, such as described in the example of FIG. 3, including anenergy storage device such as a capacitor or battery for storing theenergy generated by a respective piezoelectric elements 140. Referringto FIG. 9B, the multiple storage modules 142 may be connectedelectrically in series or parallel to deliver energy to a centralelectronics module such as TES 12, such that selected applicationelectronics within TES 12 may receive power stored by the energy storagemodules 142. Alternatively, as in FIG. 9C, each of the plurality ofenergy storage modules 142 may deliver energy to a respective localelectronics module, such as TES 12. It should be appreciated that theplurality of local electronics modules 12 may be distributed in variouslocations throughout a tire or wheel assembly and may perform similarfunctions to one another or may be configured to perform differentfunctions, such as to measure different parameters at distinctrespective locations.

While the present subject matter has been described in detail withrespect to specific embodiments thereof, it will be appreciated thatthose skilled in the art, upon attaining an understanding of theforegoing may readily produce alterations to, variations of, andequivalents to such embodiments. Accordingly, the scope of the presentdisclosure is by way of example rather than by way of limitation, andthe subject disclosure does not preclude inclusion of suchmodifications, variations and/or additions to the present subject matteras would be readily apparent to one of ordinary skill in the art.

1. A tire assembly with integrated power generation features, said tireassembly comprising: a pneumatic tire structure characterized by a crownhaving a tread portion for making contact with a ground surface, beadportions for seating said pneumatic tire structure to a wheel rim, andsidewall portions extending between each bead portion and the crown,wherein a carcass is provided within the pneumatic tire structurebetween said bead portions across said sidewall portions and said crown,wherein a belt package is provided within the crown of said pneumatictire structure between said tread portion and said carcass, and whereinan inner liner forms an interior surface of said pneumatic tirestructure; a piezoelectric device integrated with said pneumatic tirestructure and configured to generate electric charge therein upon saidtire structure being subjected to mechanical strains; a rubber patchprovided adjacent to and supporting at least one surface of saidpiezoelectric device and wherein said rubber patch is mounted to alocation selected from the group consisting of the inner liner of saidpneumatic tire structure and the exterior tread portion of saidpneumatic tire structure; at least one energy storage device coupled tosaid piezoelectric device for receiving said electric charge from saidpiezoelectric device and for storing at least some of said electriccharge therein; and an electronics assembly for monitoring tireparameters integrated with said pneumatic tire structure and coupled tosaid at least one energy storage device such that selected electroniccomponents of said electronics assembly are powered by electric chargestored in said at least one energy storage device.
 2. The tire assemblyof claim 1, wherein said piezoelectric device is embedded withinmaterial forming said pneumatic tire structure and is provided in alocation selected from the group consisting of an embedded position inthe crown of said pneumatic tire structure between said tread portionand said belt package, an embedded position in the crown of saidpneumatic tire structure between said tread portion and said beltpackage, an embedded position in the crown of said pneumatic tirestructure between said carcass and said inner liner, an embeddedposition in one of said sidewall portions of said pneumatic tirestructure between said carcass and said inner liner, an embeddedposition in one of said sidewall portions of said pneumatic tirestructure between said carcass and the tire exterior, and an embeddedposition in said zone base near a selected one of the bead portions ofsaid pneumatic tire structure.
 3. The tire assembly of claim 1, whereinsaid pneumatic tire structure further comprises a cap ply portionbetween said belt package and said tread portion, and wherein saidpiezoelectric device is embedded in the material forming the crown ofsaid pneumatic tire structure in a location selected from the groupconsisting of a location between said tread portion and said cap plyportion and a location between said belt package and said cap plyportion.
 4. The tire assembly of claim 1, wherein said belt packagecomprises first and second steel belts and wherein said piezoelectricdevice is embedded in the material forming the crown of said pneumatictire structure between said first and second steel belts.
 5. The tireassembly of claim 1, wherein said piezoelectric device comprises: aplurality of piezoceramic elements connected in one of series orparallel; a protective casing substantially surrounding said pluralityof piezoceramic elements; and first and second electrical leads forconnecting to said plurality of piezoceramic elements.
 6. The tireassembly of claim 5, wherein the polarization directions of saidplurality of piezoceramic elements are configured as one of in-phase andopposing and wherein the displacement of said plurality of piezoceramicelements are configured in one of d33 and d31 modes.
 7. The tireassembly of claim 1, wherein said electronics assembly comprises one ormore of an electronic component configured to count the number ofrevolutions said pneumatic tire structure has traveled during loss ofair pressure, a sensor configured to monitor one or more of tirepressure and tire temperature, a radio frequency (RF) device forrelaying information to a remote location, an electronic componentconfigured to measure the contact patch of the safety support duringloss of pressure to provide an indication of how severely said pneumatictire structure is under inflated, a memory device configured to storetherein information regarding the usage history of said safety support,a triggering mechanism for signaling a loss of pressure to saidpneumatic tire structure, and an electronic component configured toprovide a signal indication upon loss of pressure to said pneumatic tirestructure.
 8. A tire assembly with integrated power generation features,comprising: a non-pneumatic structurally supported tire comprising areinforced annular band, a plurality of web spokes extendingtransversely across and radially inward from the reinforced annularband, a mounting band at the radially inner end of the web spokes, and atread portion disposed on a radially outer extent of the reinforcedannular band; a piezoelectric device integrated with said non-pneumaticstructurally supported tire and configured to generate electric chargetherein upon said tire being subjected to mechanical strains; a rubberpatch provided adjacent to and supporting at least one surface of saidpiezoelectric device and wherein said rubber patch is mounted to alocation selected from the group consisting of the interior of theground contacting tread portion, the interior of the reinforced annualband, and one or more of the web spokes; at least one energy storagedevice coupled to said piezoelectric device for receiving said electriccharge from said piezoelectric device and for storing at least some ofsaid electric charge therein; and an electronics assembly for monitoringtire parameters integrated with said pneumatic tire structure andcoupled to said at least one energy storage device such that selectedelectronic components of said electronics assembly are powered byelectric charge stored in said at least one energy storage device. 9.The tire assembly of claim 8, wherein said piezoelectric device ismounted to a location selected from the group consisting of the interiorof the reinforced annular band of said non-pneumatic structurallysupported tire and one or more of the plurality of web spokes of saidnon-pneumatic structurally supported tire.
 10. The tire assembly ofclaim 8, wherein said piezoelectric device comprises: a plurality ofpiezoceramic elements connected in one of series or parallel; aprotective casing substantially surrounding said plurality ofpiezoceramic elements; and first and second electrical leads forconnecting to said plurality of piezoceramic elements.
 11. The tireassembly of claim 10, wherein the polarization directions of saidplurality of piezoceramic elements are configured as one of in-phase andopposing and wherein the displacement of said plurality of piezoceramicelements are configured in one of d33 and d31 modes.
 12. The tireassembly of claim 8, wherein said electronics assembly comprises one ormore of an electronic component configured to count the number ofrevolutions said non-pneumatic structurally supported tire has traveled,a radio frequency (RF) device for relaying selected information to aremote location, an electronic component configured to measure thecontact patch of the non-pneumatic structurally supported tire toprovide an indication of tire load levels, and a memory deviceconfigured to store information regarding the usage history of saidnon-pneumatic structurally supported tire.